Influence of hydrogen bridges on the magnetic properties of copper(II) bis(trifluoroacetate) complexes

Abstract

Copper(ll) trifluoroacetate with three coordinated water molecules and two dioxane molecules (1) crystallized as a linear chain surrounded by a net of hydrogen bonds to the dioxane and trifluoroacetate. This-complex [Cu(H2O)(3)(OOC-CF3) (2)] . 2(C4H8O2) crystallizes in the triclinic space group P1 with a= 6.067(1)Angstrom, b = 12.153 Angstrom = 15.057(3)Angstrom, alpha= 100.09(2), beta= 99.15(2), gamma= 101.00(2) and Z = 2. The single crystal EPR spectrum of (1) shows to signals (gl = 2.19 and g parallel to = 2.39), and a weak multiplet at g = 4.55. The EPR spectrum of complex (1) is interpreted as a weak exchange occurring in the chain structure found by X-ray diffraction. A hydrogen bond occurring between the axial water on one copper and the carboxylate group of a neighbor copper is proposed to transmit the magnetic exchange found by EPR. The magnetic susceptibility of (1) gave a constant value for the magnetic moment of 1.93 B.M. Bis(1,3-diaminopropan-2-ol)bis(trifluoroacetate)copper(II) complex (2) [Cu(DAP)(2)(OOC-CF3)(2)] (DAP=1,3-diamino propan-2-ol) forms a net of hydrogen bonds in the plane of the DAP ligand with adjacent trifluoroacetates. This complex crystallizes in the monoclinic space group P2(1)/c with a = 9.951(3)Angstrom, b = 8.521(2) Angstrom, c = 11.224(3)Angstrom, beta= 109.83(2) and Z = 2. Complex (2) present a weak magnetic coupling; the magnetic data fits to the Curie-Weiss equation, with theta= -3.86 K and g = 2.1. The effective magnetic moment of (2) decays steadily from 2.01 B.M. at room temperature down to 1.5 B.M. at 6 K.